This invention relates to characterizing internal pressure of a sealed container.
Food and beverage containers, for example, are often sealed under vacuum (e.g., coffee) or internally pressurized (e.g., beer). If the seal fails, the food or beverage may spoil. Accordingly, manufacturers commonly test the containers for seal integrity before shipment. One known non-intrusive testing technique is shown in Hayward U.S. Pat. No. 3,802,252, assigned to Benthos, Inc., and incorporated herein by reference; systems of this type have been sold under the name TapTone. In the Hayward scheme a can is tapped causing vibration of the lid. A microphone picks up the vibration and generates ann electrical signal which is frequency filtered. If a signal peak is found in the filtered signal, the system infers that the can seal is good.